Categories
Secondary Weather

Tropical Continental Air Mass and Saharan Dust

This morning, skies were orange/ beige across much of England as a Tropical continental (Tc) air mass brought Saharan dust. 

Saharan Dust on Windscreen

Image credit: Geoff Jenkins

Read more about why the air was carrying so much dust, and see some stunning photos from Spain and France here. The further the air travelled, the more dust was deposited and the less dust remained in the air – so the most vivid skies were in the south. 

Read our guide to air masses for background information or show our YouTube explainer

weather chart 16th March 2022

How can you tell that there is Tc air from this weather chart (midnight on 16th March 2022)? 

The air approximately follows the isobars, shown as thin lines on this chart. To work out which way, you need to look at the pressure systems and remember that air goes clockwise around anticyclones (H) and anticlockwise around cyclones (L). 

Considering either the 962mbar Low or the 1033mbar High shows you that the air is coming from the south (a southerly wind) across England.

Following the isobar marked 1020 back, you can see that the air has come over Spain from Africa. This is a Tropical continental air mass.

Behind the occluded front, for much of Ireland, the wind coming from the west. The 1020mbar Low is a bit misleading, but you can see that the air coming up from the south diverts to curve round it in an anticlockwise flow. 

Tc weather chart
Categories
Research Science Secondary

Resources for Mars Day

Mars not dusty

14th March 2022 is Mars Day

Establishing the radiation or energy budget of the Earth has been crucial to understanding climate change, but what do the radiation budgets of Mars and other planets in our solar system look like? Read about it in this article from Physics Review or this one from Science in School

You can find the energy budget images for all the planets mentioned here

Categories
Books Secondary

Book Review: the Weather Detectives

Weather Detectives
 
The Weather Detectives
Author: Michael Erb
Year: 2021
Publisher: Tumblehome, Inc. 
Suggested age range: 9-12
Price: £11.99
Set in the Caribbean, this book sees two young people and their associates set out to investigate some mysterious stories surrounding a cruise ship and its captain. 
Interspersed through the story are excepts from a weather guide being written by one of the characters. In many ways these are the best bits of the book – engaging and well written. It’s just a shame that they don’t really link in to the story.  Given the title, I was expecting the weather, or these asides, to provide clues which the protagonists could use to solve the mystery. 
It was tricky to suggest an age range for this book. The plot line is not very sophisticated, and it’s a short read, but the vocabulary is quite advanced in places. Fans of other mysteries aimed at this age range, such as those written by Lauren St. John, Lauren Child or Robin Stevens, would be disappointed.  
Written for an American audience, the only issue for a reader from another country would be not knowing what the IRS (Internal Revenue Service) is – one of the ‘clues’ is related to this.  
The author has written other books and supplied some suggested related activities at https://www.weatherdetectives.org
Categories
Climate Change Secondary

New Resource for International Women’s Day 2022

Sustainable development goals 5 and 13

We have created a new resource in time for International Women’s Day 2022, exploring the links between two of the Sustainable Development Goals – gender equality, and climate action.

Taking information from this weeks’ InterGovernmental Panel on Climate Change (IPCC) report on Impacts, Adaptation and Vulnerability as well as some of the relevant highlights fromCOP26, teachers can adapt the resource to suit their class. 

 

Categories
Extreme weather Geography Secondary Weather

Storm Eunice and Generic Case Study Template

Storm Eunice cloud and wind

We have created a new worksheet which allows students to collect information and create a case study of a named UK storm. As part of the worksheet, students collect and annotate weather chart and other information about the storm including weather warnings. 

Storm Eunice is given as a worked example. 

Categories
Geography Schools Secondary Teaching Weather

New Films: Air Masses and the ITCZ

We have made two new explainer films which can be seen on YouTube:

An Introduction to Air Masses

All About the InterTropical Convergence Zone (ITCZ)

 
global rainfall patterns
Categories
CPD Geography Schools Secondary

Resources Highly Commended by SAGT

SAGT award

We are delighted that our “Weather and Climate: a Teacher’s Guide” resource has been awarded a Highly Commended in the Book Category for this year’s Scottish Association of Geography Teachers (SAGT) Publishers’ Awards.

Categories
Blog Geography Secondary Teaching Weather

Air Masses

In this article we explore air masses – the idea that, by looking at where our wind is blowing from, and what has happened to the air in the wind on its way to use, we can begin to understand why we’re getting some particular weather.

We live on an island, and the weather can come at us from any direction, although in practice, it comes from some directions more than others  – this wind rose shows the direction the wind was recorded coming from at Heathrow airport, near London. The longer the bar, the more often the wind came from that direction, so you can see that our wind comes from between southwest and west most often.  

Lets take a step back and remember that warm air rises – whether that’s the air being heated in a hot air balloon or the air above a radiator (watch a simple demonstration).

What happens to the rising air? As it rises it cools. Cloud and rain are caused by warm air rising, warm air rising is called convection (watch a simple demonstration).

You can often see convection going on in the atmosphere – you get puffy cumulus clouds, with flattish bases and puffy tops where the cloud is bubbling up.

clouds

More generally, Clouds form when there is more condensation going on than evaporation in the atmosphere.

The colder it is, the less evaporation happens – so cloud forms when the air cools.

This isn’t just when warm air rises.

Now we can think about air masses, they are classified according to where they have come from, and what they have passed over:

UK air masses

One air mass generally covers the whole country.

However, it can bring different weather conditions to different places. For example, Tropical continental air can carry Saharan dust, but it mostly falls on the south of the UK – there isn’t much left in the air by the time it reaches Scotland.

Lets consider Polar maritime (Pm) air first (click on the map to start the animation):

Polar maritime air comes towards us from further North in the Atlantic. It starts cold, but is slowly warmed by the ocean below as it travels over progressively warmer water. It also picks up moisture from the ocean. 

As it is warmed, it becomes more unstable and inclined to rise, leading to convection and puffy Cumulus clouds, mainly over the ocean. As the air hits land (the western coast of Ireland, Wales, Scotland and England) the air, which was already inclined to rise, is forced up a bit more – forming more cloud, and giving rise to rainfall. 

Polar maritime air, our dominant air mass, brings cloud and rain to the west of the UK and relatively dry air to the east. 

This satellite image is typical of Pm air – you can see the puffy cumulus clouds over the ocean, and the belt of cloud over the western side of the country.  

Returning Polar maritime air (rPm) is air which is Polar in origin but which swings round to hit the UK from the west or even slightly south of west – but if you were to follow its path back, you would see that it was Polar. 

Arctic maritime (Am) air is extreme Polar maritime air, coming down to the UK straight from the north, over the Arctic ocean. It tends to bring wintry weather to Scotland and isolated snowy showers further south, triggered by air rising over the local orography. 

Polar Continental (Pc) air will also be cold to start with and get progressively warmer as it moves south, so you would also expect convection. However, the air will be very dry as it passes over continental Europe, so little cloud will form. The UK is a set of islands though and to reach us, the air must pass over the North Sea, picking up water vapour as it does so. The cloud and precipitation (typically snow in winter) it brings therefore primarily affect the east coast. The longer the path it takes over the North Sea, the more precipitation there will be. 

This satellite image is typical for Pc air – you can see the cloud free areas immediately to the west of the land masses, with cloud forming further east (ignore the front to the west of the UK and Ireland).

Of course, the characteristics of the air masses can be very different in the summer and the winter. Siberia, for example, is extremely cold in winter but relatively warm in summer – so a polar continental air mass can bring us bitterly cold weather and heavy snowfall (for eastern counties) in the winter, but much warmer weather in the summer.

The processes at work in Tropical Maritime (Tm) air are a bit different. This is warm air, which is being cooled from below as it moves north. You therefore wouldn’t expect any convection with air rising, cooling and forming cloud. However, the air is being cooled just by moving north and so eventually may reach the temperature at which cloud forms – flat, featureless sheets of stratus cloud because, on the whole, the air is staying at the same level.

As it is maritime air, there is plenty of water vapour available to form cloud droplets. The processes which give us big, fat raindrops are mainly associated with the vertical air motion and circulations in cumulus clouds. So Tm air at best gives a persistent drizzle.

The satellite image below shows the extensive sheet of stratus cloud over the Atlantic associated with Tm air.

We rarely experience Tropical Continental (Tc) air – air that flows up from the Sahara over continental Europe.  This is the warmest and driest air we can get – any moisture picked up over the Mediterranean will be rained out before it reaches us.

Tc air gives clear skies, as you can see in the satellite image below – again ignore the front to the west of the UK. In the summer, this can mean that some areas get particularly warm – maybe because of their colour (dark) or aspect (facing the Sun) – giving rise to late afternoon localised thunderstorms

A front is where two air masses meet. In the UK, the weather fronts associated with depressions usually separate polar and tropical maritime air.

If there is a front, then different parts of the UK can be experiencing different air masses. The weather on the fronts themselves is more extreme. 

Look out of the window now – what cloud types can you see? Does that tell you anything about where the air is coming from? You can have a look at earth.nullschool to see if you are right.

 

 

Categories
Climate Change Extreme weather Geography Secondary

New Teaching Resource – Salt Marsh Evidence

We have just added a new resource to our Weather and Climate: a Teachers’ Guide collection in the Changing UK Climate section. 

The resource provides students with source material, graphs and maps to allow them to make a poster explaining how salt marshes can protect coastal areas from the impact of rising sea levels. 

Steart Marshes – designed for adaptation to climate change.

Categories
Climate Change Rain Secondary

Exploring Amazon Rainfall data

deforestation

We are delighted to have worked together with the RGS to produce a resource for A Level geography students, using key data skills to investigate the impact of Amazon deforestation on rainfall. 

The worksheet is designed to highlight the importance of meteorology understanding in physical geography. There are activities on the statistical tests of Mann Whitney U-Test and Spearman’s Rank Correlation Coefficient.

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